Telephone companies have in recent years been increasing the range of features offered to subscribers, and in order to easily make use of those features, telephone sets having displays and feature accessing pushbuttons have come into common use. Examples of such telephone sets are SUPERSET 4.TM. and other versions of that family of telephone sets. Each telephone set version has a different arrangement and number of pushbuttons from another in order to enable easy operation of particular features. The displays are used for composing and receiving messages, and for displaying the function of "soft keys", whose designation changes depending on the feature or step in a sequence invoked by a user, or as commanded by software programs. Other displays indicate the status of telephone line pushbuttons, such as ringing, busy, idle, hold, etc.
The SUPERSET.TM. series of telephone sets has been designed as "dumb" sets, that is, they merely react to commands sent to them for operation from the switching system to which they are connected. The switching system contains programs which, when enabled, cause the displays to operate, cause the switching system to send signals in response to the detection of the depression of pushbuttons, etc. The status of each display indicator and each character in the display is formulated at the switching system and is transmitted as a signal to each telephone set. Other telephone sets may be "intelligent" in that at least some software programs are stored within the telephone set and are invoked upon receiving commands from the switching system for operating the display, sending signals, etc.
Whether the telephone sets are dumb or intelligent, whether the telephone set operation programs are stored within the telephone set, within the peripheral control system associated with the switching system, or whether they are stored in a memory associated with a central processor for controlling the switching system, the operation programs for driving particular forms of telephone sets are specific to each type of telephone set. The result is that if a subscriber desires to upgrade or downgrade his telephone set (i.e. to be able to access a greater number or fewer number of features), there must be change to the operating or driving software specific to that telephone line. In addition, in case other versions of telephone sets become available which have variations of features, different combinations of features or different features from those previously contemplated, a significant change in the operating software is required. Thus when changes to accommodate changed or new forms of telephone sets are required to be effected, significant cost is incurred.
It should be noted that in this specification the term "switching system" is intended to mean any form of communication system which utilizes peripherals, whether using time division or space division switching, communication via a network such as a local area network, etc. Peripherals is intended to mean telephone sets, trunks, special service circuits, etc.